Pumps



Oct. 18, 1955 E, w. DOWNING PUMPS Filed May 31. 1950 Z 221161272501 Elli) United States Patent Ofiice PUMPS Handsworth Wood, Birmingham, Joseph Lucas Limited, Birming- Eric William Downing, England, assignor to ham, England This invention relates to reciprocatory pumps, and particularly pumps required for supplying liquid fuel to an internal combustion engine, or lubricant to a machine, the object of the invention being to provide an improved pump of the kind in which the delivery stroke is effected by a spring.

The invention comprises the combination of a spring loaded piston, and a hollow plunger adapted to effect the suction stroke of the piston and to serve as the delivery valve.

In the accompanying drawings:

Figures 1 and 2 are sectional elevations illustrating two embodiments of the invention.

Referring to Figure 1, a hollow body part a has formed therein a cylindrical bore b containing a piston c which is loaded by a spring d through an abutment e contained in a chambered portion of the body part as shown. The inlet port 1 is provided in the body part adjacent to one end of the said bore. Through the said end of the bore extends a reciprocatory plunger g of smaller diameter than the piston. The plunger is loaded by a spring I: and is actuated in the direction for imparting the suction stroke to the piston by a rotary cam i, acting through a thrust piece j. In the plunger is formed an axial passage k leading from the inner end of the plunger to a transverse passage m, which opens into a circumferential groove it around the plunger, this groove being in constant communication with a delivery passage in the body of the pump.

The arrangement is such that during the suction stroke of the piston the inner end of the plunger g is in contact with the piston c, and the entrance to the passage k in the plunger is thereby closed. After the piston has been moved suificiently to open the inlet port f, liquid flows into the bore during the continued movement of the plunger and piston. During the return movement of the plunger under the action of its spring h, the piston follows it under the action of its spring d until the inlet port is reclosed. The plunger g then leaves the piston, since the motion of the latter is retarded due to the resistance encountered in the delivery passage, Whereas the motion of the plunger continues under the action of the spring h as permitted by the cam i. This movement of the plunger away from the piston opens the inner end of the axial passage k in the plunger. The piston 0 can now (under the action of its spring d), discharge liquid from the bore b and through the plunger passage to the outlet 0 at a rate dependent on the force exerted by the spring a and the resistance encountered in the delivery passage. This resistance may depend on the amount of opening of a control valve, or of a metering device, situated between the pump and the engine.

The end of the plunger g adjacent to the piston 0 may be chamfered as shown in which case, the fluid pressure in the bore b during the delivery stroke of the piston assists the spring h in moving the plunger.

In the construction shown in Figure 2, the flow of liquid into the bore b is controlled by an inlet valve in- Patented Oct. 18, 1955 corporated with the piston. In this example the piston c is made hollow and within it is secured in any convenient manner, such as by a spring ring p, a plug q. As shown the plug q is of smaller diameter than the interior of the piston c, and is formed at one end with a flange 4 through the medium of which the plug is secured to the piston by the spring p, the flange being notched at q to establish communication between the bore b and the annular space t between the plug and the inner periphery of the piston. Between the adjacent forward ends of the plug and piston is contained a freely movable closure piece r which can close the holes s in the piston end. Liquid entering at the inlet 1 can during the suction stroke pass through the holes 5 and along the annular space I to the bore b. During the delivery stroke the closure piece r closes the holes s, and the liquid is discharged to the outlet 0 in the manner above described. The suction stroke is effected by the action of the cam i on the end of the plunger g remote from the piston c. The delivery stroke is effected by the spring d which acts on the piston c through the abutment e. During the first part of the delivery stroke the liquid pressure created in the bore b not only causes the closure piece r to close the holes s, but also acts on the chamfered inner end of the plunger g to separate the latter from the piston c for establishing communication between the bore b and the axial passage k in the plunger, this passage being in constant communication with the outlet 0 through the transverse passage m and the circumferential groove 11 in the plunger. The above described separation of the plunger g from the piston c is controlled by the cam 1'.

Either of the above described constructions may itself form a complete pump, or it may form a unit of which a plurality are combined to form a multi-cylinder pump.

By this invention I am able to provide a variable delivery pump in a very simple form. Whilst the invention is primarily intended for use as a liquid fuel pump, it may be used for supplying lubricating oil, or for any other analogous purpose in which it is required that the delivery shall be automatically variable in response to the demand for the liquid supplied by the pump.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A liquid pump comprising in combination a body part having a bore therein, a reciprocatory piston in said bore, a reciprocatory plunger arranged coaxially with and adjacent to said piston for effecting movement thereof in one direction, said plunger being formed with an axial passage which at one end is closable by said piston during movement of the latter by said plunger, a spring acting on said piston for eflfecting movement thereof in the opposite direction, a liquid inlet, means for isolating said liquid inlet from said bore during movement of said piston by said spring, a liquid outlet, passage means establishing constant communication between said liquid outlet and the end of said axial passage remote from said piston, actuating means for imparting movement to said plunger in the direction for actuating said piston, and thereby causing liquid from said inlet to enter said bore, and means whereby said plunger is separable from said piston under the control of said actuating means to establish communication between said bore and said axial passage, and thereby permit said piston to discharge liquid from said bore through said outlet, during movement of said piston under the action of said spring.

2. A liquid pump according to claim 1, in which the means for isolating the liquid inlet from the bore in the body part is formed by a part of the piston.

3. A liquid pump according to claim 1, in which the piston is of hollow form and contains a valve forming the means for isolating the liquid inlet from the bore in the body part, the valve being movable to a closed position by pressure of liquid in said bore during movement of said piston by the spring. 7

4. A liquid pump according to claim 1, in which the means whereby the plunger is separable from the piston comprises a spring acting on said plunger.

' 5. A liquid pump'according to claim 1, in which the means whereby the plunger is separable from the piston is formed by the end of said plunger adjacent to said piston, said end being shaped to permit liquid pressure created by said piston in the bore of the body part to act on said plunger in the direction for effecting separation thereof from said piston.

UNITED STATES PATENTS Kooperstein Feb. 23, 1926 Lurcott June 21, 1927 Wilkinson Apr. 12,1932 Bischof Jan. 30, 1934 Steiner Aug. 13, 1935 Steiner Aug. 13, 1935 Scribner May 11, 1937 Huber Sept. 14, 1948 Nieolls May 2,1950 

